Microstructural evolution and FCC twinning behavior during hot deformation of high temperature titanium alloy Ti65

Abstract

Although the development of titanium alloys with working temperatures above 600 ℃ faces enormous difficulties and challenges, the related research has not stopped. In the present work, detailed analyses on microstructure evolution and hot deformation behavior of a new temperature resistant 650 ℃ titanium alloy Ti65 were investigated from micrometer scale to nanometer scale. The results revealed that lamellar α grains gradually fragmentized and spheroidized during the α + β phase region compression and the orientation of the c-axis of α grains gradually aligned to radial directions, forming two high Schmid factors (SFs) value texture eventually with the increase of strain to 0.7. Moreover, there were some strengthening characters in the α + β phase region such as lenticular αs and nano silicide (TiZr)6Si3. In the β phase region, fine equiaxed dynamic recrystallized (DRX) β grains were formed. Besides, the variant selection of α´ martensite followed Burgers orientation relationship during the compression process. The main deformation mechanisms of the α + β phase region were dislocation slip and orientation dependent spheroidization. Whereas, the deformation process in the β phase region was controlled by β grain DRX. Interestingly, many nano scale FCC twins were generated at the interface of α´ lath during deforming in the β phase region, which was firstly observed in Ti65 alloy.